Safety concepts in geotechnical engineering then and now - how do the Eurocodes affect tunnelling?

As indicated in the title, many different safety concepts - in the sense of various definitions of "safety" and "safety factor" - have been used in civil engineering and particularly in geotechnical engineering according to the type of project. "The" old safety concept (single) is a fiction. The Eurocodes are based on a common basis, the semi-probabilistic concept, but as before demand different strategies for different tasks. Different strategies for ultimate limit states of failure are now described in geotechnical engineering as different "design approaches".
For retaining structures, which include tunnel linings in the broadest sense, the design approach DA 2⋆ is the most practical for standard cases and involves the least work in the transition to the Eurocodes. This procedure is also intended as standard in the Austrian guideline RVS 9.01.42 "Tunnel structures in soft soil under built-up areas" in the 2004 issue. This guideline is being revised at the moment, but no significant changes are anticipated in the new issue.
Particular features of geotechnical engineering, e.g. that ground can be an action as well as construction material or resistance, have resulted in some special provisions in Eurocode 7. Some of these particular features are referred to in this paper. The application of the Eurocodes in connection with numerical calculations in tunnel construction is also investigated and the limits discussed. The introduction of the Eurocodes is seen as a chance to exploit the experience in all European countries for better codes, unified safety requirements and to jettison ballast.